Fuse



A. STEENMYER FUSE 2 Sheets-*Sheet 2 Filed May 14, 1931 |NvENToR 4341/0/ xfff/'lmayd/ @WiWi/17 ATTORNEY Patented Mar. 27, 1934 UNITED STATES PATENT OFFICE FUSE iii-:ISSUED Application May 14, 1931, Serial No. 537,267

6 Claims.

'I'his invention relates to fuses and is particularly directed to an expulsion type of fuse structure and fuse link therefor.

One of the many difllculties involved in the 5 use of expulsion type fuses is due to the fact that these fuses are often called upon to interrupt currents which are not very large. For instance, in farm line service the load is usually small and is often anon-inductive load. Under these 10 conditions the usual types of expulsion fuses do not give entirely satisfactory results, for frequently the current is only sufficient to rupture a small portion of the fuse without causing complete expulsion, thus causing subsequent leakage and carbonization which -often results in complete destruction of the fuse structure. ',In addition, these leaks cause radio interference.

While this invention is not tobe construed as limited to low capacity expulsion fuses, it never- 2o theless is eminently suitable for such use and overcomes the defects noted above.

Objects ofthis invention are to provide an expulsion fuse which will insure complete and adequate separation of the severed portions of the fuse, even if the fuse is only slowly melted; which will have in addition an expulsion action thus securing quick clearing of the fuse for large overloads; which insures clearing of the fuse for both small and large overloads, and renders this clearingV of the fuse, or opening of the circuit,

certain and sure under all conditions of operation.

` Further objects are to provide-a fuse which closely conforms in dimensions to the standard type of expulsion fuses; which does not require an elaborate and expensive construction; which secures both the advantages of 'an expulsion action and also of a spring action in insuring separation of the severed portions of the fuse;

4o and in which the major parts, with the excep- K tion of the fusible section, are uninjured during operation, and may be used over and over.

Further objects are'to provide an expulsion type of fuse which, in certain forms, is so constructed that a telltale or visible dication is Embodiments of the invention are shown in the accompanying drawings, in which:-

Figure 1 is a view, partly in section, of one form of the invention.

Figure 2 is a fragmentary view showing the position of the parts after the fuse has blown.

Figure 3 is an enlarged detail of the upper portion of the link.

Figure 4 is a plan view of the structure shown in Figure 3, with parts broken away.

Figure 5 is a modified form of attaching means for the upper end of the fuse link.

Figure 6 is a somewhat diagrammatic view showing how the upper end of the fuse link may be cut to cooperate with the type of fastening means shown in Figure 5.

Figure 7 is a view, partly in section, showing a modified form of fuse.

Figure 8 is a sectional view showing a still further form of fuse.

Referring to the drawings, particularly Figures 1 to 4, it will be seen that the expulsion fuse comprises a fuse cartridge of insulating material which may comprise theinsulating tube 1, or which may be formed of a plurality of tubes in accordance with any of the standard constructions. This phase of the fuse construction forms no portion of the invention, and for the sake 'of clearness a single tube has been shown.

The expulsion fuse is provided with an upper contact 2 and a lower contact 3. The upper contact may consist of a sleeve threaded upon the upper end of the tube and is itself provided with a reduced externally threaded upper end 4. A metallic cap 5 is screwed upon this reduced end and serves to clamp the upper end of the fuse link in place. The lower Contact surrounds the tube and is locked thereto 'in any suitable manner. It is provided with a pair of spaced ears 6 between which the lower end of the fuse link is passed. A threaded, knurled thumb screw '7 is in threaded engagement with the ears 6, and serves to clamp the lower end of the fuse link in place.

The fuse link in the form shown in Figures 1 to 4 comprises a fusible section 8 which may comprise an upper and a lower ribbon or wire of metal, preferably a high resistance alloy such as nickel-silver. It is also to be noted that the upper and lower ends 9 and 10 of the fusible secp under small overloads the low melting point solder is fused, whereas under high overloads it is frequently the case that the major portion of the ribbons themselves are fused. At least under the latter condition an expulsion action takes place. Somewhat of an expulsion action takes place even under small overloads. However. it frequently happens that under very small overloads, the full benet of the expulsion action is not secured. This defect, however, is cured and eliminated by the structure hereinafter described, which is associated with, the fusible section and forms a part of the fuse link.

The enlarged upper portion of the fuse link is preferably provided with an upper reversely y folde/d Yportion 1l, which is clamped between the two plates 12 of an upperbutton or contact clip,

'the upper and lower portions of the clip being joined, as shown in Figure 4, and the lower portion Vbeing apertured to permit the passage ltherethrough of the upper end of the portion 9, see particularly Figures 3 and 4.

The lower portion of lthe fusible section is joined to a relatively rigid section 13 which may consist of arelatively rigid wire, as indicated in Figures 1, 2 and 3. This wire may be attached to the lower end of the fusible section in any suitable manner, as by means of the small screw 14. Any other mode of attachment may, of course, be used if it `is found preferable. However, vthe use of the screw is desirable to permit ready substi-l tution or" new fusible sections, as it seldom occurs that any other portion of the fuse is damaged when rupture occurs.

The wire 13 or relatively rigid section, is elongated, and preferably at a point intermediate its end a helical spring 15 is attached. 'I'his helical spring is attached at its lower end to a relatively strong, flexible copper' leader 16, which is clamped by means of the screw 7 to the lower contact 3. The ends of the rod 13 and the leader 16 are joined by means of a very flexible copper leader 17 located preferably within the helical spring 15. Electrically, 'the leaders 17 and 16 constitute the conducting means for carrying the current from the rod 13 to the lower contact 3, thereby preventing heating of the spring -due to the passage of the current.

In view of the fact that these fuses are frequently used on farm lines and similar locations where the load is relatively small and is usually of a non-inductive nature, it is frequently the case that the overload lis only of small value. Even under these conditions complete and wide separation of the severed portions of the fusible section is obtained by the construction described. For example, when the fuse blows, the spring draws the rod 13 downwardly thus aiding in the separation of the severed portion of the fusible section, such action of the spring assisting in any expulsion action that takes place at this time. Obviously the spring and rod do not interfere with the expulsion action of the fuse structure under considerable overload, but rather assist in the adequate separation of the severed portion of the fusible section.

By means of this'construction' a very large gap is 3obtained, and consequently there is no leakage that takes place after the fuse has blown. This avoids the heretofore serious defect in certain types of fuses due to leaking of the current between relatively closely positioned v,severed sections of the fusible portion of the link. This leaking, as is well known, frequently destroys the and extends outwardly below the lower open end v of the tube 1, thus acting as a telltale. It is prevented from passing completely from the tube by means of the leader 16. A comparison of Figures 1 and 2 will show the action of the fuse very clearly.

The partial retention of the rod or rigid mem-4 ber 13 within the tube is very desirable. Consider on the other hand, what would happen if `the spring were vnot strengthened, or held or guided by the rod 13. It would be projected outwardly from the tube and would dangle loosely fromthe lower portion of the structure. In view of its relative flexibility, it might readily be blown into other live portions of adjacent structures, or against a grounded section, or it might inadvertently contact with a lineman undertaking to renew the fuse. However, by means of the construction illustrated the complete expulsion of the spring and adjacent parts is prevented.

It is to be noted from Figures 5 and 6 that the upper end 9 of the fusible section is preferably provided with a slot or opening 18. The purpose` of thisconstruction is to allow a customer to cut the upper end of the .fusible section olf, as shown in dotted lines in Figure 6, and to thereafter slip the resulting prongs of the fusible section on opposite sides of a screw 19 secured to a contact button 20, or to any other support as the case may be. In other words, this type of construction of the fusible section permits its use with at least two different types of upper attaching means.

Referring to Figure 7 where a modified form of the invention is disclosed, it will be seen that the same general inventive idea has been followed. The 'fusible section 21 may be of 'the same general type as that previously described and is locked to the upper-contact 2 in any suitable manner, for instance by means of the cap 5. The lower end of the fusible section is attached to the upper end of a spring 22 and is also attached to a flexible copper leader 23 extending downwardly through the spring.

This spring is partially housed and received by a fiber or other insulating tube 24, which is attached to the spring adjacent the lower end of the tube 24 and the spring 22, as clearlyshown in the lower portion of Figure 1. The tube 24 acts as the substantially rigid member corresponding roughly to 'the rod 13 previously described. The lower end of the spring 22, the leader 23 and the tube 24 are attached by means of a relatively strong copper leader 25 to the lower contact 3.

The operation of this fuse is substantially the same as that previously described. AUpon blowing of the fuse, the spring insures adequate separation of the severed portion of the fusible section and the rigid tube 24 projects partially from the lower end of the insulating cartridge or tube 1.

The fusible section 21 may be of the "same or of a different type from that previously described.

In the form of the invention shown in Figure 8, a-relatively rigid rod 26 is attached to the lower leader 27, and intermediate the ends of the rod 26 a helical spring 28 is secured. A flexible copno way-interferes with the expulsion action of 1` the fuse, but materiallyjassists in the separation ofv the severed portion of the fusible element.

:petasse per leader 29eirtends from the upper endof the Y rod 26 to the lower end of the fusible'section 30.

ywire -bein'g preferred. As shown inFigure 8, a

single strand of wire has been shown for illus tration. n

At this point it is-to be distinctly understood that any suitable-type of fusible sectionmay be employed.' Forfexample; in any forms of the invention any one 'of the several forms of fusible sections may be used in place of those specifically shown, or any other type'of .fusible section may inner tube with 'an outer porcelain tube, al-

though this speciic phase of the construction forrnsno'portion of the invention.

. Furtherv it is to` be vdistinctly understood that while Figure '1 shows the preferred form of construction, that nevertheless other types of fusible sections may be employed, or other types of k construction conforming to the general'spirlt of the-invention herein discussed.

- 44It will be seenlthatja novelform of expulsion fusel and fuse link' therefor hasv been disclosed,

`in which adequate-separationof the severed porn tion of the fusible sectionis insured, irrespective of whether'the overload. is small lor large, `and it will be noted further that the actionv of the spring Fromactual tests `conducted with this apparatus, it'has been found that in by far the larger number vof cases no damagevis done to anyportion ofthe fuse structure -when the fuse blows,

i other than the ."fusible section', and that ,the parts may be 'used-over and over, the fusible section 'care for.

alone being renewed.

Itwill be seen further that a verysimple type of construction has been provided by this invention which is eminently practical, which may be cheaply made, and which isaeasy to renew and Althoughthis invention has been described in considerable detail, it is-to be understood that such description is 'intended as illustrative rather than limiting, as the invention may be variously :embodied and is to be interpreted as claimed. 'Iiclaiin:

1. .A fuse link comprising a fusible section, a relatively rigid section, a exible conducting section, and a helical spring coaxial with said relatively rigid section, said spring and said relatively rigid section being coextensive for at east a pori tion of their respective lengths.

2. A fuse link comprising' aV fusible section, a relatively rigid section, a exibleconducting section, and a helical spring guidedby said relatively rigid section and telescopically associated with said relatively rigid section;

3. A fuse comprising a non-extensible tube having an open lower end and having contacts adjacent each end; a fuse link carried within said tube and joining said contacts, said link comprising a fusible section, a relatively rigid elongated section, and a exible section, and a spring secured to` said relatively rigid section, said relatively rigid section being telescopically related to said spring. l

4. An expulsion fuse comprising a tube having an open lower end and having an upper contact and a lower contact; a fuse link in said tube and joining said contacts, said link having a fusible portion and a relatively rigid portion; and a spring for separating the severed portions of said fusible portion when said fuse blows, said relatively rigid portion of said link projecting downwardly from the open end of said tube when said fusible portion is ruptured.

5. An expulsion fuse comprising a tube having preventing said relatively rigid portion from passing completely from said' tube. l

6. An expulsion fuse comprising a tube having upper and lower contacts, a fuse linkjoining said contacts and having an upper fusible portion located in the upper portion of said tube, a spring for aiding, during the expulsion action of said fuse, in the separation of the severed portions .of

said link, and means for preventing the expulsion of theentire length of the spring from said tube. 

